Indian Institute Of Technology



MHRD Govt. Of India


Creep Transient Based On Obstacle Distance ...


Objective

To study the effect of obstacle distance on the creep transient behavior of materials.

Virtual Experiments


Schematic diagram showing effect of obstacle distance on the creep deformation of a material

Please Select one of the following to view the behavior

0.60μm 0.88μm 1.10μm

Introduction

Obstacle is something which blocks your path. Roadblocks etc. could serve as artificial obstacles while a mental block is a good example of a non physical obstacle which is a more potent force than any of the obstacles mentioned above. However, when we are dealing with dislocations we are operating at a micron scale and obstacles to dislocation motion could be precipitates, grain boundaries or other dislocations as well. Obstacle need not be some physical object blocking the path it could be a force generated due to some reaction at some totally different location. Just as we go around, over or through an obstacle, dislocations might as well take one of these paths to overcome the obstacles. The obstacle size, distribution, etc. effect the energy required to overcome the obstacle. A decrease in obstacle distance leads to an increase in the number of obstacles encountered by dislocations during their motion and since energy is required to overcome an obstacle higher the number of obstacles more is the energy required to overcome these obstacles. This leads to lowering of creep deformation since a major portion of the deformation energy is consumed in overcoming of the obstacles.

Methodology

In this experiment random numbers are assigned to dynamic variables at each time interval to study the microscopic and dynamic behavior of various systems on the principles of Monte Carlo simulation. Here each element is characterized by slip probability and strength parameter 's'. The concept of transfer of load to neighboring sites when slip occurs i.e. load shedding is considered.
The model assumes that strain hardening and recovery processes can be ignored for small strain regime and materials with low hardening rates, that obstacle density and its behavior does not change during the deformation process and that materials respond to plastic deformation similarly because the observed behavior is due to a large number of discrete events coupled through load transfer.

Results

Following are the creep transient results for some of the obstacle distances which have been tested:
0.60μm
0.88μm
1.10μm

Conclusions

Click the following link for conclusions:
Conclusions